John McCain's compelling victory in Tuesday's New Hampshire Republican presidential primary sent shockwaves through American politics yesterday, as the Arizona senator promised to take his "great national crusade" against big money politics all the way to the White House in November.

Mr McCain trounced the party frontrunner, Texas governor George W Bush, in New Hampshire, the traditional first primary of the election year, and left the remaining conservative runners scrambling for survival in what is now to all intents and purposes a two-horse Republican race.

The scale of Mr McCain's win astonished even his own pollsters and posed serious questions about Mr Bush's strategy and chances. Mr McCain took 49% of the Republican vote, followed by Mr Bush on 31%. Steve Forbes finished third on 13%, followed by Alan Keyes on 6% and Gary Bauer on 1%.

"Thank you, thank you, thank you, thank you," a beaming Mr McCain told cheering supporters at his Nashua headquarters, with his wife Cindy at his side. "The wonderful New Hampshire campaign has come to an end but a great national crusade has just begun."

In the Democratic contest, vice-president Al Gore dug out a narrow but significant victory, defeating former senator Bill Bradley by 52% to 47%. Mr Gore has won both early contests, in Iowa and New Hampshire, but Mr Bradley did well enough this week to pre-empt expected calls from Democratic party elders for him to abandon his presidential bid before the March 7 "Super Tuesday" primaries.

Most of the political attention yesterday focused on the aftermath of the McCain-Bush contest, with both men wasting no time in hurrying to campaign in South Carolina, the site of their next head-to-head battle in the February 19 Republican primary.

Mr McCain won in New Hampshire because he focused his effort in a single state. While Mr Bush spent the last few months building a richly financed campaign around the United States, Mr McCain worked New Hampshire, spending 73 campaign days there against Mr Bush's 37.

New Hampshire was tailor-made for the iconoclastic, voter-friendly former Vietnam war prisoner. Unusually among primary states, New Hampshire allows independent voters to participate in either of the party contests, and these voters flocked to Mr McCain's cause. The Arizona senator won a 3-1 victory over Mr Bush among independents.

But Mr McCain also won in practically every other category of voters too, including a particularly important 44%-36% win over Mr Bush among registered Republicans, an outcome that stunned the Texas governor and the party hierarchy almost as much as the overall result itself.

In defeat, Mr Bush was quick to contrast his own "50-state strategy" with Mr McCain's state-by-state approach. "He ran a really good race and a strong race," Mr Bush said in his concession speech. "He spent more time in this great state than any of the other candidates and it paid off.

"The road to the Republican nomination and the White House is a long road. Mine will go through all 50 states and I intend it to end at 1600 Pennsylvania Avenue [the White House]."

New Hampshire voters provided a disappointing night for the three conservative contenders, especially Mr Bauer, who is expected to drop out soon. Mr Forbes, though, is likely to continue, thus limiting Mr Bush's hopes of rallying the whole of the conservative vote against Mr McCain's progressive challenge.

The Republicans now embark on a frenetic schedule of campaigning and fundraising. Mr Bush has so far amassed $69m in funds, compared with Mr McCain's $14m, enabling the Texas governor to spend heavily on the crucial television advertising that now becomes a much more important campaign weapon than the up-close-and-personal tactics of New Hampshire.